Heat exchangers are commonly used to remove heat from fluids. In the context of the automotive field, for example, it is well-known to use heat exchangers as oil coolers, to transfer heat from engine oil or transmission fluid to engine coolant.
One known type of oil cooler is constructed from a stack of thin-gauge metal plates. The plates are formed such that, in the stack, interstices are formed, the plates and interstices being disposed in alternating relation. The interstices define a plurality of oil passages and a plurality of coolant passages. The oil passages and the coolant passages are disposed in the stack in alternating relation. Thus, each plate separates a respective oil passage from a respective coolant passage, thereby to conduct heat between any contents of the oil passage and any contents of the coolant passage when a temperature differential exists therebetween. The oil passages are coupled to one another in parallel to provide an oil flow path, and the coolant passages are coupled to one another in parallel to provide a coolant flow path. Thus, when a flow of relatively hot oil is delivered to the oil flow path and a flow of relatively cold coolant is delivered to the coolant flow path, a flow of relatively cool oil and a flow of relatively warm coolant results.
As is well known, the heat transfer efficiencies of such structures is a function of the temperature differential between the fluid inlet and outlet, and the relative direction of flow of the fluids passing through the structures.
Normally, it is necessary to manufacture a variety of heat exchangers of varied dimensions to provide heat transfer performance suitable for a particular application in which it is to be employed. However, this necessitates relatively short production runs, which has an associated cost. As well, flexibility for a given application demands that a variety of heat exchangers be on hand, which has an associated inventory cost. Modern manufacturing is very cost-sensitive, and as such, these costs are disadvantageous.
In United States Patent Application Publication No. US 2002/0129926 A1, (Yamaguchi), published Sep. 19, 2002, it is taught to divide the plurality of oil passages into three groups; connect the oil passages of each group in parallel to form a respective oil flow subpath; and connect the oil flow subpaths in series. This provides a heat exchanger wherein the oil path is three times the length and one third the width than that of a heat exchanger of otherwise identical structure wherein all of the oil passages are connected in parallel, and which therefor has heat exchange characteristics differing therefrom. In this reference, which employs a plurality of plates including apertures for forming manifolds for oil and coolant, such separation is attained by omitting the openings in selected plates. This structure arguably overcomes in part the problem of short production runs, since a variety of heat exchangers can be provided simply by altering the number and position of the plates in which openings are omitted. However, this structure does not overcome the problem of inventory cost associated with flexibility.